1. Field of the Invention
The invention relates to a viewfinder for reflex cameras, and is more particularly directed to a focusing screen plate within a viewfinder device.
2. Description of the Prior Art
In viewfinders for reflex cameras, it has been the practice to cause a light flux passed from an object through an objective lens to be reflected by a mirror, such as a quick-return mirror or the like, and directly focused on a mat surface provided on that side of a focusing screen plate adjacent to the mirror. Thus, there is only a reflecting surface present between the objective lens through which the light flux from the object passes and the mat surface on which the light flux is focused. However, to meet the growing demand for cameras which are compact and light in weight, consideration has been given to reversing the direction of the focusing screen plate; that is, to provide the mat surface on that side of the focusing screen plate opposite from the mirror so as to permit the light flux to be focused thereon. Such a construction is advantageous in making the camera body compact and light in weight. However, there is the disadvantage that a body corresponding to the thickness of the focusing screen plate intervenes, and therefore, the focusing condition is disturbed. The result is that even if the objective lens is free of aberration, the formed image is out of focus in the marginal portion thereof although the point of focus is coincident with the center portion of the mat surface. This leads to inconvenience in the setting of the composition of the picture; also, there is difficulty in judging the out-of-focus condition of the object image resulting from stop-down.